Refrigeration apparatus



ug:c 2% 1950 R. E. TOBEY REFRIGERATION APPARATUS Filed Dec. 19, 1946 Ffm. 2.

INVENTOR RAYMa/vo E. TeA-35V. BWM ATTORNEY Fmi Si,

Patented Aug. 22, 1950 UNITED STATES PATENT OFFICE REFRIGERATION APPARATUS Raymond E. Tobey, Springfield, Mass., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application December 19, 1946, Serial No. 717,135

8 Claims. l

This invention relates to refrigeration apparatus and more especially to a defrost signal for such apparatus, and is a continuation-in-part of my application, Serial No. 682,430, filed July 9, 1946, since abandoned.

It is an object of this invention to provide a novel signal to indicate that the refrigerating apparatus needs defrosting.

It is a further object of this invention to provide a novel defrost signal which has no moving parts.

These and other objects are effected by the invention as will be apparent from the following description and claims taken in connection with the accompanying drawings, forming a part of this application, in which:

Fig. 1 is a front elevation of the interior of a refrigerator embodying the invention with the indicator showing no signal;

Fig. 2 is a somewhat similar view but with the defrost indicator showing a signal;

Fig. 3 is a section on the line III-III of Fig. 2 but with the refrigerator door closed; and

Fig. 4 is a sectional view of a modification of the invention.

Referring to the drawings for a detailed description of the invention, the reference numeral Ill designates a refrigerator cabinet having an outer metal shell I2, an inner liner I4, and heatinsulating material I6 packed between the outer shell I2 and the inner liner I4 to insulate the cabinet. vertical edge of the cabinet Ill.

An evaporative cooling unit 20, maintained at a temperature of about zero degrees Fahrenheit, is located in the upper portion of the cabinet and provides a chamber for the freezing and storing of frozen foods. The cooling unit 20 is provided with refrigerant passages 22 to cool the same and with a door 24 to close the front thereof and substantially lls the upper portion of the cabinet, leaving only small air spaces along the side walls, the upper and the rear wall, and the door 24 of the cooling unit. A defrost tray 28 is located below the cooling unit 20 and the lower portion of the refrigerator is provided with shelves 30 for the storage of foods at a temperature of about forty degrees Fahrenheit.

The defrost indicator 32 of this invention is set into a rectangular opening 34 in the door 24 of the cooling unit 20. The indicator 32 comprises a metal plate 3S on which letters 44 are embossed to form the word Defrost A plastic material 38 of low heat conducting quality is molded over the embossed letters 44 of the plate An insulated door I8 is hinged on the I36 in such a manner that the embossed letters 44 lie close to the exterior surface 42 of the material 3B, but are covered by the material so that they are invisible. The plastic material 38 preferably is of a color which contrasts with the white frost, the preferred color being black. The indicator 32 is secured to the door 24 so that the material 38 projects through the opening 34 and the plate 36 lies on the interior of the cooling unit 20 with its marginal portions 40 overlapping the door 24.

With this arrangement, the outer surface 42 of the material 38 will becooled unevenly with the portions covering the embossed letters 44 being colder than the remaining portions of the surface 42. The portions covering the letters 44 are cooled to below freezing temperature by thev the cooling unit 20. The heat conducting capacity of the plate 36 and the thickness of the plastic material 3B at the embossed letters 44 of the plate 36 are preferably so proportioned that frost gathers on the surface 42 opposite the letters 44 only when the frost on the\sides of the cooling unit 20 is of such thickness that defrosting is required. With this construction, it will be apparent that the word "Defrost appears in the nature of a white frost on the outer black surface 42 of the plastic material'38 when the cooling unit requires defrosting.

A modification of the invention is shown in Figure 4 and like parts are provided with the same reference numerals. In this modification, the plastic material 5I) is similar to the plastic material 38 of Figure 3 except that its front surface 52 is flush with the front surface 54 of the embossed letters 44 formed in the plate 36. The plastic material 50 may be of any color.

A thin panel 56 of plastic material of poor conductivity and of a color contrasting with frost is secured by tap screws 58 to the plastic material 50 and is spaced slightly from the front surface 54 thereof byvwashers 60 encircling the screws 58 to form an air gap 62. The gap 62 is open to the circulation of the air in the cabinet I0 so that the humidity of the air will condense on the front surface 54 of the letters 44 as a frost. As the frost increases in thickness, it bridges the gap 62 and increases the heat conduction between the letters 44 and the portions of the panel 56`directly in front of them so that corresponding letters 'in frost form on the front surface of the panel 3 building up the bridging frost between the letters u and the panel 5I is not visible.

The thickness of the frost which has collected on the cooling unit 20 when the word Defrost" appears on the panel 50 can be regulated by varying the width of the gap I2. This can be effected by using washers 60 of a thickness corresponding to the desired width of the air gap Il. An increase in the width of the air gap 62 will result in an increase in the thickness of the frost on the cooling unit 20 when the word Defrost"`appears on the panel 5B.

It will be apparent from the above that the defrost signal of this invention is devoid of any mechanically moving parts.

While the invention has been shown in several form's, it will be obvious to those skilled in the art that lt is not so limited, but is susceptible of various other changes and modifications without departing from the spirit thereof.

What is claimed is:

l. In a refrigerator having an insulated food storage chamber, a cooling unit adapted to be maintained at below freezing temperatures and exposed to the air in said chamber to cool the same, the combination with said cooling unit of material having a surface exposed to the air of :aid chamber, said surface being of a color con- ;rasting with frost, said cooling unit being in intimateheat exchange relationship with only a. portion of said surface to cool said portion to below freezing temperatures, whereby frost collecting on this portion when the cooling unit is maintained at below freezing temperatures is clearly visible by contrast with the color of the remainder of the surface.

2. In a refrigerator having an insulated food storage chamber, a cooling unit adapted to be maintained at below freezing temperatures and exposed to the air in said chamber to cool the same, the combination with said cooling unit of material of low heat conductivity having a surface exposed to the air of said chamber, said surface being of a color contrasting with frost, said cooling unit being in intimate heat exchange relationship with only a portion of said surface to cool said portion to below freezing temperatures. whereby frost collecting on this portion when the cooling unit is maintained at below freezing temperatures is clearly visible by contrast with the color of the remainder of the surface.

3. In a refrigerator having an insulated food storage chamber, a cooling unit adapted to be maintained at below freezing temperatures and exposed to the air in said chamber to cool the same, the combination with said cooling unit of material of low heat conductivity having a surface exposed to the air of said chamber, said surface being of a color contrasting with frost, means for conducting heat from said material at points adjacent to only certain portions of said surface to cool said portions of said surface to below freezing temperatures, said means conducting said heat to said cooling unit, whereby frost collecting on said portions' when the cooling unit is maintained at below freezing temperatures forms a visual signal on said contrasting surface.

4. The refrigerator deflned in claim 3 wherein said portions of the surface are maintained at a higher temperature than said cooling unit so that a light coating of frost on said portions indicates that a heavy coating of frost has formed on said unit.

5. In a refrigerator having an insulated food storage chamber including a door, a cooling lmit adapted to be maintained at below freezing temperatures and exposed to the air in said chamber to cool the same, the combination with said cooling unit of material of low heat conductivity having a surface facing said door and exposed to the air of said chamber, said surface being of a color contrasting with frost, means for conductlng heat from said material at points adjacent to only certain portions of said surface to cool said portions to below freezing temperatures, said means conducting said heat to said cooling unit, whereby frost collecting on said portions when the cooling unit is m'aintained at below freezing temperatures forms a visual signal on said contrasting surface.

6. In a refrigerator having an insulated food storage chamber with an access opening, a door fox said opening, a cooling unit adapted to be maintained at a temperature below freezing and exposed to the air in said chamber, the combination with said cooling unit of a material of low heat conductivity positioned in said chamber, said material having a surface facing said access opening and of a color contrasting with frost, metallic heat-conducting means positioned between a portion of said material and said evaporator to cool said portion te below frosting temperatures when the cooling unit is maintained at below freezing temperatures, said portion including a portion of said surface, the area of said surface immediately surrounding said surface portion being so remote from said cooling unit and from said heat-conducting means that its temperature is above the temperature at which frost gathers thereon, said heat-conducting means being of such heat-conducting capacity that the temperature of said surface portion when the cooling unit is maintained at below freezing temperatures is reduced to such a degree that a visible coating of frost forms thereon when the layer of frost on said cooling unit is so heavy that defrosting of the cooling unit is beneficial to the operation of said refrigerator.

'1. In a refrigerator having an insulated food storage chamber with an access opening, a door for said opening, a cooling unit adapted to be maintained at a temperature below freezing and exposed to the air in said chamber so that the water vapor of said air tends to condense on said cooling unit in the form of frost, the combination with said cooling unit of a thin panel of poor heat-conducting material having a front surface of a color contrasting with frost and a rear surface, said panel being positioned in said chamber with its front surface facing said access opening, heat-conducting means in heat transfer relationship with said cooling unit and positioned near but spaced from the rear surface of a portion of said panel, the space between said means and said portion being normally open to the circulation of air in said chamber, said space being of such width and said heat-conducting means of such capacity that when the cooling unit is maintained at below freezing temperatures, the frost forming on said means bridges said space and cools said portion of said panel to such a temperature that frost collects on the front surface of said portion, the areas of said panel immediately surrounding said panel portion being in such poor heat conducting relationship with said cooling unit that the temperature of said areas is above the point at which frost forms thereon.

8. In a refrigerator having an insulated food 5 storage chamber with an access opening, a door for said opening, a cooling unit adapted to be maintained at a temperature below freezing and exposed to the air in said chamber, the combination with said cooling unit of poor heat conducting material, said material having a front surface facing said access opening, and means spaced rearwardly from a portion of said surface for conducting vsuilicientheat from said portion to said cooling unit to cause frost to form on said portion, the remaining portions of said front surface being in such poor heat conducting relationship with said cooling unit that said remaining portions are above the temperature at which frost forms thereon.

RAYMOND E. TOBEY.

6 ness crm The following references are of record in the ille o! this patent:

UNITED STATES PATENTS Number Name Date 1,917,048 Midgley July 4, 1933 2,073,106 Hull Mar. 9, 1937 2,200,801 Money May 14, 1940 10 2,225,932 Shaw Dec. 24, 1940 

